Inductively coupled RF plasma reactor and plasma chamber enclosure structure therefor

ABSTRACT

A plasma chamber enclosure structure for use in an RF plasma reactor. The plasma chamber enclosure structure being a single-wall dielectric enclosure structure of an inverted cup-shape configuration and having ceiling with an interior surface of substantially flat conical configuration extending to a centrally located gas inlet. The plasma chamber enclosure structure having a sidewall with a lower cylindrical portion generally transverse to a pedestal when positioned over a reactor base, and a transitional portion between the lower cylindrical portion and the ceiling. The transitional portion extends inwardly from the lower cylindrical portion and includes a radius of curvature. The structure being adapted to cover the base to comprise the RF plasma reactor and to define a plasma-processing volume over the pedestal. The structure being formed of a dielectric material of silicon, silicon carbide, quartz, and/or alumina being capable of transmitting inductive power therethrough from an adjacent antenna.

RELATED APPLICATIONS

[0001] This application is a divisional of Ser. No. 09/675,319 filedSep. 29, 2000 by Kenneth S. Collins et al., herein incorporated byreference, which is a divisional of Ser. No. 08/648,254 filed on May 13,1996 by Kenneth S. Collins et al., herein incorporated by reference,which is a continuation-in-part of the following co-pending U.S.applications, the disclosures of which are incorporated herein byreference:

[0002] (a) Ser. No. 08/580,026 filed Dec. 20, 1995 by Kenneth S. Collinset al. which is a continuation of Ser. No. 08/041,796 filed Apr. 1, 1993by Kenneth S. Collins et al. which is a continuation of Ser. No.07/772,340 filed Jun. 27, 1991;

[0003] (b) Ser. No. 08/503,467 filed Jul. 18, 1995 by Michael Rice etal. which is a divisional of Ser. No. 08/138,060 filed Oct. 15, 1993;and

[0004] (c) Ser. No. 08/597,577 filed Feb. 2, 1996 by Kenneth Collins,which is a continuation-in-part of Ser. No. 08/521,668 filed Aug. 31,1995 (now abandoned), which is a continuation-in-part of Ser. No.08/289,336 filed Aug. 11, 1994, which is a continuation of Ser. No.07/984,045 filed Dec. 1, 1992 (now abandoned). In addition, U.S.application Ser. No. 08/648,256 filed May 13, 1996 by Kenneth S. Collinset al. entitled “Plasma Reactor With Heated Source of aPolymer-Hardening Precursor Material” discloses related subject matter.

BACKGROUND OF THE INVENTION

[0005] 1. Technical Field

[0006] The invention is related to inductively coupled RF plasmareactors of the type having a reactor chamber ceiling overlying aworkpiece being processed and an inductive coil antenna adjacent theceiling.

[0007] 2. Background Art

[0008] Inductively coupled RF plasma reactors are employed to perform avariety of processes on workpieces such as semiconductor wafers.Referring to FIG. 1, one type of inductively coupled RF plasma reactorhas a reactor chamber 10 including a ceiling 12 and a cylindrical sidewall 14. A pedestal 16 supports the workpiece 18, such as asemiconductor wafer, so that the workpiece generally lies in a workpiecesupport plane, and a bias RF power generator is coupled to the pedestal16. A generally planar coil antenna 20 overlies the ceiling 12 and iscoupled to a plasma source RF power generator 22. A chief advantage ofinductively coupled RF plasma reactors over other types such ascapacitively coupled ones, is that a higher ion density can be achievedwith the inductively coupled type.

[0009] Adequate etch selectivity is achieved by operating at higherchamber pressure. (The term etch selectivity refers to the ratio of etchrates of two different materials exposed to etching in the reactor.)This is because the polymerization processes typically employed in ahigh density plasma etch reactor to protect underlyingnon-oxygen-containing (e.g., silicon, polysilicon or photoresist) layersduring etching of an overlying oxygen-containing (e.g., silicon dioxide)layer are more efficient at higher chamber pressures (e.g., above about20-500 mT) than at lower pressures. Polymer precursor gases (e.g.,fluorocarbon or fluorohydrocarbon gases) in the chamber tend topolymerize strongly on non-oxygen-containing surfaces (such as siliconor photoresist), particularly at higher chamber pressures, and onlyweakly on oxygen-containing surfaces (such as silicon dioxide), so thatthe non-oxygen-containing surfaces are relatively well-protected frometching while oxygen-containing surfaces (such as silicon dioxide) arerelatively unprotected and are etched. Such a polymerization processenhances the oxide-to-silicon etch selectivity better at higher chamberpressures because the polymerization rate is higher at higher pressuressuch as 100 mT. Therefore, it is desireable to operate at a relativelyhigh chamber pressure when plasma-etching oxygen-containing layers overnon-oxygen-containing layers. For example, under certain operatingconditions such as a chamber pressure of 5 mT, an oxide-to-photoresistetch selectivity of less than 3:1 was obtained, and raising the pressureto the 50-100 mT range increased the selectivity to over 6:1. Theoxide-to-polysilicon etch selectivity exhibited a similar behavior.

[0010] The problem with increasing the chamber pressure (in order toincrease etch selectivity) is that plasma ion spatial densitydistribution across the wafer surface becomes less uniform. There aretwo reasons this occurs: (1) the electron mean free path in the plasmadecreases with pressure; and (2) the inductive field skin depth in theplasma increases with pressure. How these two factors affect plasma ionspatial density distribution will now be explained.

[0011] With regard to item 1 above, the electron-to-neutral specieselastic collision mean free path length, which is inversely proportionalto chamber pressure, determines the extent to which electrons can avoidrecombination with other gas particles and diffuse through the plasma toproduce a more uniform electron and ion distribution in the chamber.Typically, electrons are not generated uniformly throughout the chamber(due, for example, to a non-uniform inductive antenna pattern) andelectron diffusion through the plasma compensates for this and providesgreater electron and plasma ion spatial density distribution uniformity.(Electron spatial density distribution across the wafer surface directlyaffects plasma ion spatial density distribution because plasma ions areproduced by collisions of process gas particles with energeticelectrons.) Increasing chamber pressure suppresses electron diffusion inthe plasma, thereby reducing (degrading) plasma ion spatial densitydistribution uniformity.

[0012] This problem may be understood by reference to FIG. 1, in whichthe inductive antenna 20, due to its circular symmetry, has an antennapattern (i.e., a spatial distribution of the magnitude of the inducedelectric field) with a null or local minimum along the antenna axis ofsymmetry so that very few if any electrons are produced over the wafercenter. At low chamber pressures, electron diffusion into the space(“gap”) between the antenna 20 and the workpiece 18 is sufficient totransport electrons into the region near the wafer center despite thelack of electron production in that region, thereby providing a moreuniform plasma distribution at the wafer surface. With increasingpressure, electron diffusion decreases and so plasma ion distributionbecomes less uniform.

[0013] A related problem is that the overall plasma density is greaternear the ceiling 12 (where the density of hot electrons is greatest)than at the workpiece 18, and falls off more rapidly away from theceiling 12 as chamber pressure is increased. For example, the electronmean free path in an argon plasma with a mean electron temperature of 5eV at a chamber pressure of 1 mT is on the order of 10 cm, at 10 mT itis 1.0 cm and at 100 mT it is 0.1 cm. Thus in a typical application, fora 5 cm ceiling-to-workpiece gap, most of the electrons generated nearthe ceiling 12 reach the workpiece at a chamber pressure of 1 mT (for amaximum ion density at the workpiece), and a significant number at 10mT, while at 100 mT few do (for a minimal ion density at the workpiece).Accordingly, it may be said that a high pressure regime is one in whichthe mean free path length is about {fraction (1/10)} or more of theceiling-to-workpiece gap. One way of increasing the overall plasma iondensity at the workpiece 18 (in order to increase etch rate and reactorthroughput) without decreasing the chamber pressure is to narrow the gapso that the mean free path length becomes a greater fraction of the gap.However, this exacerbates other problems created by increasing chamberpressure, as will be described further below.

[0014] With regard to item (2) above, the inductive field skin depthcorresponds to the depth through the plasma—measured downward from theceiling 12—within which the inductive field of the antenna 20 is nearlycompletely absorbed. FIG. 2 illustrates how skin depth in an argonplasma increases with chamber pressure above a threshold pressure ofabout 0.003 mT (below which the skin depth is virtually constant overpressure). FIG. 2 also illustrates in the dashed-line curve howelectron-to-neutral elastic collision mean free path length decreaseslinearly with increasing pressure. The skin depth function graphed inFIG. 2 assumes a source frequency of 2 MHz and an argon plasma densityof 5□10¹⁷ electrons/m³. (It should be noted that the correspondingplasma density for an electro-negative gas is less, so that the curve ofFIG. 2 would be shifted upward with the introduction of anelectro-negative gas.) The graph of FIG. 2 was derived using a collisioncross-section for an electron temperature of 5 eV in argon. (It shouldbe noted that with a molecular gas such as C₂F₆ instead of argon, thecollision cross-section is greater so that the skin depth is greater ata given pressure and the entire curve of FIG. 2 is shifted upward.) Ifthe chamber pressure is such that the inductive field is absorbed withina small fraction—e.g., {fraction (1/10)}th—of the ceiling-to-workpiecegap adjacent the ceiling 12 (corresponding to a pressure of 1 mT for a 5cm gap in the example of FIG. 2), then electron diffusion—throughout theremaining {fraction (9/10)}ths of the gap—produces a more uniform plasmaion distribution at the workpiece surface. However, as pressureincreases and skin depth increases—e.g., beyond about {fraction(1/10)}th of the gap, then electron diffusion tends to have less effect.Thus, a measure of a high skin depth regime is that in which the skindepth is at about {fraction (1/10)} or more of the source-to-workpiecegap length. For example, if the pressure is so great that skin depthequals the ceiling-to-workpiece spacing (corresponding to a pressure ofabout 100 mT for a 5 cm gap in the example of FIG. 2), then any antennapattern null or local minimum extends to the surface of the workpiece18, effectively preventing electron diffusion from compensating for theeffects of the antenna pattern null on the processing of the workpiece.Such problems can arise, for example, when the ceiling-to-workpiecespacing is decreased in order to increase overall plasma density at theworkpiece surface. A related problem with a small ceiling-to-workpiecespacing and a high chamber pressure is that electrons are lost not onlyto recombination with particles in the processing gas but are also lostto recombination by collisions with the surface of the ceiling 12 andthe workpiece 18, so that it is even more difficult for electronsgenerated in other regions to diffuse into the region adjacent theworkpiece center.

[0015] In summary, plasma ion density at the wafer can be enhanced byreducing the gap between the axially symmetrical antenna/ceiling 20, 12and the workpiece 18. But if the gap is reduced so much that theinductive field skin depth becomes a substantial fraction (≧10%) of thegap, then ion density at the workpiece center falls off significantlyrelative to the edge due to the antenna pattern's center null. However,for a smaller fraction of skin depth over gap and sufficient electrondiffusion (characteristic of a low chamber pressure), electrons producedfar from the workpiece center may diffuse into the center region beforebeing lost to gas phase recombination or surface recombination, therebycompensating for the antenna pattern's center null. But as the gap isreduced (to increase overall plasma density at the workpiece) andchamber pressure is increased (to enhance etch selectivity), then: (1)the induced electric field over the workpiece center approaches a nullso that no electrons are produced in that region, and (2) electronsproduced in other regions generally cannot diffuse to the workpiececenter region due to recombination with gas particles and chamber (e.g.,ceiling) surfaces.

[0016] Thus, as the wafer-to-coil distance is decreased by the reactordesigner (in order to enhance plasma density near the wafer surface, forexample), the plasma ion density decreases at the wafer center andultimately, at very short wafer-to-antenna distances, becomes a centernull giving rise to an unacceptable process non-uniformity. For example,in a plasma etch process carried out in such a reactor, the etch rate atthe wafer center may be so much less than elsewhere that it becomesimpossible to perform a complete etch across the entire wafer surfacewithout over-etching near the wafer periphery. Conversely, it becomesimpossible to avoid over-etching at the wafer periphery withoutunder-etching the wafer center. Thus, the problem is to find a way todecrease the wafer-to-antenna distance without incurring a concomitantpenalty in process non-uniformity.

[0017] One approach for solving or at least ameliorating this problem isdisclosed in U.S. application Ser. No. 08/507,726 filed Jul. 26, 1995 byKenneth S. Collins et al. and entitled “Plasma Source with anElectronically Variable Density Profile”, which discloses that an outergenerally planar coil antenna 24 coupled to a second independentlycontrolled plasma source RF power generator 26 can be provided over theceiling 12 concentric with the inner coil antenna 20 of FIG. 1. Theefficacy of this solution can be seen from the graphs of FIGS. 3Athrough 3E. FIG. 3A illustrates the plasma ion density as a function ofradius from the center of the workpiece 18 for a workpiece-to-ceilingheight of 4 inches (10 cm), the curve labelled A being the ion densityproduced by the outer coil antenna 24 and the curve labelled B being theion density produced by the inner coil antenna 20. The total resultingplasma ion density is the sum of these two curves but is not depicted inthe drawing for the sake of simplicity. FIG. 3A shows that at a heightof 4 inches (10 cm), the outer coil antenna 24 produces a uniform plasmaion density distribution, the inner coil antenna 20 not being required.FIG. 3B corresponds to FIG. 3A for a reduced workpiece-to-ceiling heightof 3 inches (7.5 cm), and shows that a dip in plasma ion densityproduced by the outer coil antenna 24 is compensated by thecenter-dominated ion density produced by the inner coil antenna 20. FIG.3C corresponds to FIG. 3A for a further reduced workpiece-to-ceilingheight of 2.5 inches (6.25 cm), and shows that the compensation by theinner coil 20 for the center dip in the plasma ion density produced bythe outer coil 24 remains fairly effective as the workpiece-to-ceilingheight is further reduced, although a slight dip in the total resultingplasma ion density near the center would begin to appear below thisheight. As shown in FIG. 3D, a further reduction in workpiece-to-ceilingheight to only 1.25 inches (about 3.2 cm) yields a pronounced dip in theplasma ion densities produced by both the inner and outer coil antennas20, 24, so that there is very little compensation and the resultingplasma ion density (the sum of the two curves shown) is highlynon-uniform. As shown in FIG. 3E, the problem worsens as the height isfurther reduced to 0.8 inches (2 cm).

[0018] What FIGS. 3A-3E show is that even the use of inner and outercoil antennas to solve the problem of the null in plasma ion densitynear the workpiece center may lose effectiveness as theworkpiece-to-ceiling height is reduced below certain values. Thus, thewafer-to-ceiling height cannot be reduced below a factor of the skindepth without sacrificing process uniformity. On the other hand, unlessthe wafer-to-ceiling height can be so reduced, plasma density andprocess performance is limited. Accordingly, there is a need for a wayto reduce the workpiece-to-ceiling height without sacrificing processuniformity.

SUMMARY

[0019] A plasma chamber enclosure structure for use in an RF plasmareactor which includes a pedestal adapted to support a workpiece to beprocessed, a reactor base housing the pedestal, and a coil antennaadjacent the reactor and which is adapted to inductively couple RF powerinto the reactor. The plasma chamber enclosure structure being asingle-wall dielectric enclosure structure of an inverted cup-shapeconfiguration. The plasma chamber enclosure structure having a ceilingwith an interior surface of substantially flat conical configurationextending to a centrally located gas inlet such that when positionedover the base said interior surface is more distant from the pedestalover a center of the pedestal and closer to the pedestal over aperiphery of the pedestal.

[0020] The plasma chamber enclosure having a sidewall with a lowercylindrical portion generally transverse to the pedestal when positionedover the base and a transitional portion between the lower cylindricalportion and the ceiling. The transitional portion extends inwardly fromthe lower cylindrical portion and includes a radius of curvature.

[0021] The plasma chamber enclosure structure being adapted to cover thereactor base to define a plasma-processing volume over the pedestal andcomprise the RF plasma reactor. The plasma chamber enclosure structurebeing capable of transmitting inductive power therethrough from anadjacent antenna. The plasma chamber enclosure structure being formed ofa dielectric material of silicon, silicon carbide, quartz, and/oralumina.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 is a cut-away side view of an inductively coupled plasmareactor of the type employed in a co-pending U.S. patent applicationreferred to above employing generally planar coil antennas.

[0023]FIG. 2 is a log-log scale graph of induction field skin depth in aplasma in cm (solid line) and of electron-to-neutral elastic collisionmean free path length (dashed line) as functions of pressure in torr(horizontal axis).

[0024]FIG. 3A is a graph of plasma ion density as a function of radialposition relative to the workpiece center in the reactor of FIG. 1 for aworkpiece-to-ceiling height of 4 inches, the curves labelled A and Bcorresponding to plasma ion densities produced by outer and inner coilantennas respectively.

[0025]FIG. 3B is a graph of plasma ion density as a function of radialposition relative to the workpiece center in the reactor of FIG. 1 for aworkpiece-to-ceiling height of 3 inches, the curves labelled A and Bcorresponding to plasma ion densities produced by outer and inner coilantennas respectively.

[0026]FIG. 3C is a graph of plasma ion density as a function of radialposition relative to the workpiece center in the reactor of FIG. 1 for aworkpiece-to-ceiling height of 2.5 inches, the curves labelled A and Bcorresponding to plasma ion densities produced by outer and inner coilantennas respectively.

[0027]FIG. 3D is a graph of plasma ion density as a function of radialposition relative to the workpiece center in the reactor of FIG. 1 for aworkpiece-to-ceiling height of 1.25 inches, the curves labelled A and Bcorresponding to plasma ion densities produced by outer and inner coilantennas respectively.

[0028]FIG. 3E is a graph of plasma ion density as a function of radialposition relative to the workpiece center in the reactor of FIG. 1 for aworkpiece-to-ceiling height of 0.8 inches, the curves labelled A and Bcorresponding to plasma ion densities produced by outer and inner coilantennas respectively.

[0029]FIG. 4A is a cut-away side view of a plasma reactor in accordancewith an alternative embodiment of the invention employing a singlethree-dimensional center non-planar solenoid winding.

[0030]FIG. 4B is an enlarged view of a portion of the reactor of FIG. 4Aillustrating a preferred way of winding the solenoidal winding.

[0031]FIG. 4C is a cut-away side view of a plasma reactor correspondingto FIG. 4A but having a dome-shaped ceiling.

[0032]FIG. 4D is a cut-away side view of a plasma reactor correspondingto FIG. 4A but having a conical ceiling.

[0033]FIG. 4E is a cut-away side view of a plasma reactor correspondingto FIG. 4D but having a truncated conical ceiling.

[0034]FIG. 5 is a cut-away side view of a plasma reactor in accordancewith the preferred embodiment of the invention employing inner and outervertical solenoid windings.

[0035]FIG. 6 is a cut-away side view of a plasma reactor in accordancewith a second alternative embodiment of the invention corresponding toFIG. 5 in which the outer winding is flat.

[0036]FIG. 7A is a cut-away side view of a plasma reactor in accordancewith a third alternative embodiment of the invention corresponding toFIG. 4A in which the center solenoid winding consists of plural uprightcylindrical windings.

[0037]FIG. 7B is a detailed view of a first implementation of theembodiment of FIG. 7A.

[0038]FIG. 7C is a detailed view of a second implementation of theembodiment of FIG. 7A.

[0039]FIG. 8 is a cut-away side view of a plasma reactor in accordancewith a fourth alternative embodiment of the invention corresponding toFIG. 5 in which both the inner and outer windings consist of pluralupright cylindrical windings.

[0040]FIG. 9 is a cut-away side view of a plasma reactor in accordancewith a fifth alternative embodiment of the invention corresponding toFIG. 5 in which the inner winding consists of plural upright cylindricalwindings and the outer winding consists of a single upright cylindricalwinding.

[0041]FIG. 10 is a cut-away side view of a plasma reactor in accordancewith a sixth alternative embodiment of the invention in which a singlesolenoid winding is placed at an optimum radial position for maximumplasma ion density uniformity.

[0042]FIG. 11 is a cut-away side view of a plasma reactor in accordancewith a seventh alternative embodiment of the invention corresponding toFIG. 4A in which the solenoid winding is an inverted conical shape.

[0043]FIG. 12 is a cut-away side view of a plasma reactor in accordancewith an eighth alternative embodiment of the invention corresponding toFIG. 4A in which the solenoid winding is an upright conical shape.

[0044]FIG. 13 is a cut-away side view of a plasma reactor in accordancewith a ninth alternative embodiment of the invention corresponding toFIG. 4A in which the solenoid winding consists of an inner uprightcylindrical portion and an outer flat portion.

[0045]FIG. 14 is a cut-away side view of a plasma reactor in accordancewith a tenth alternative embodiment of the invention corresponding toFIG. 10 in which the solenoid winding includes both an inverted conicalportion and a flat portion.

[0046]FIG. 15 is a cut-away side view of a plasma reactor in accordancewith an eleventh alternative embodiment of the invention correspondingto FIG. 12 in which the solenoid winding includes both an uprightconical portion and a flat portion.

[0047]FIG. 16 illustrates another embodiment of the invention employinga combination of planar, conical and dome-shaped ceiling elements.

[0048]FIG. 17A illustrates an alternative embodiment of the inventionemploying a separately biased silicon side wall and ceiling andemploying electrical heaters.

[0049]FIG. 17B illustrates an alternative embodiment of the inventionemploying separately biased inner and outer silicon ceiling portions andemploying electrical heaters.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] In a plasma reactor having a small antenna-to-workpiece gap, inorder to minimize the decrease in plasma ion density near the centerregion of the workpiece corresponding to the inductive antenna patterncenter null, it is an object of the invention to increase the magnitudeof the induced electric field at the center region. The inventionaccomplishes this by concentrating the turns of an inductive coiloverlying the ceiling near the axis of symmetry of the antenna andmaximizing the rate of change (at the RF source frequency) of magneticflux linkage between the antenna and the plasma in that center region.

[0051] In accordance with the invention, a solenoidal coil around thesymmetry axis simultaneously concentrates its inductive coil turns nearthe axis and maximizes the rate of change of magnetic flux linkagebetween the antenna and the plasma in the center region adjacent theworkpiece. This is because the number of turns is large and the coilradius is small, as required for strong flux linkage and close mutualcoupling to the plasma in the center region. (In contrast, aconventional planar coil antenna spreads its inductive field over a wideradial area, pushing the radial power distribution outward toward theperiphery.) As understood in this specification, a solenoid-like antennais one which has plural inductive elements distributed in a non-planarmanner relative to a plane of the workpiece or workpiece support surfaceor overlying chamber ceiling, or spaced at different distancestransversely to the workpiece support plane (defined by a workpiecesupporting pedestal within the chamber) or spaced at different distancestransversely to an overlying chamber ceiling. As understood in thisspecification, an inductive element is a current-carrying elementmutually coupled with the plasma in the chamber and/or with otherinductive elements of the antenna.

[0052] A preferred embodiment of the invention includes dual solenoidalcoil antennas with one solenoid near the center and another one at anouter peripheral radius. The two solenoids may be driven at different RFfrequencies or at the same frequency, in which case they are preferablyphase-locked and more preferably phase-locked in such a manner thattheir fields constructively interact. The greatest practicaldisplacement between the inner and outer solenoid is preferred becauseit provides the most versatile control of etch rate at the workpiececenter relative to etch rate at the workpiece periphery. The skilledworker may readily vary RF power, chamber pressure andelectro-negativity of the process gas mixture (by choosing theappropriate ratio of molecular and inert gases) to obtain a wider rangeor process window in which to optimize (using the present invention) theradial uniformity of the etch rate across the workpiece. Maximum spacingbetween the separate inner and outer solenoids of the preferredembodiment provides the following advantages:

[0053] (1) maximum uniformity control and adjustment;

[0054] (2) maximum isolation between the inner and outer solenoids,preventing interference of the field from one solenoid with that of theother; and

[0055] (3) maximum space on the ceiling (between the inner and outersolenoids) for temperature control elements to optimize ceilingtemperature control.

[0056]FIG. 4A illustrates a single solenoid embodiment (not thepreferred embodiment) of an inductively coupled RF plasma reactor havinga short workpiece-to-ceiling gap, meaning that the skin depth of theinduction field is on the order of the gap length. As understood in thisspecification, a skin depth which is on the order of the gap length isthat which is within a factor of ten of (i.e., between about one tenthand about ten times) the gap length. FIG. 5 illustrates a dual solenoidembodiment of an inductively coupled RF plasma reactor, and is thepreferred embodiment of the invention. Except for the dual solenoidfeature, the reactor structure of the embodiments of FIGS. 4A and 5 isnearly the same, and will now be described with reference to FIG. 4A.The reactor includes a cylindrical chamber 40 similar to that of FIG. 1,except that the reactor of FIG. 4A has a non-planar coil antenna 42whose windings 44 are closely concentrated in non-planar fashion nearthe antenna symmetry axis 46. While in the illustrated embodiment thewindings 44 are symmetrical and their symmetry axis 46 coincides withthe center axis of the chamber, the invention may be carried outdifferently. For example, the windings may not be symmetrical and/ortheir axis of symmetry may not coincide. However, in the case of asymmetrical antenna, the antenna has a radiation pattern null near itssymmetry axis 46 coinciding with the center of the chamber or theworkpiece center. Close concentration of the windings 44 about thecenter axis 46 compensates for this null and is accomplished byvertically stacking the windings 44 in the manner of a solenoid so thatthey are each a minimum distance from the chamber center axis 46. Thisincreases the product of current (I) and coil turns (N) near the chambercenter axis 46 where the plasma ion density has been the weakest forshort workpiece-to-ceiling heights, as discussed above with reference toFIGS. 3D and 3E. As a result, the RF power applied to the non-planarcoil antenna 42 produces greater induction [d/dt][N·I] at the wafercenter—at the antenna symmetry axis 46—(relative to the peripheralregions) and therefore produces greater plasma ion density in thatregion, so that the resulting plasma ion density is more nearly uniformdespite the small workpiece-to-ceiling height. Thus, the inventionprovides a way for reducing the ceiling height for enhanced plasmaprocess performance without sacrificing process uniformity.

[0057] The drawing of FIG. 4B best shows a preferred implementation ofthe windings employed in the embodiments of FIGS. 4A and 5. In orderthat the windings 44 be at least nearly parallel to the plane of theworkpiece 56, they preferably are not wound in the usual manner of ahelix but, instead, are preferably wound so that each individual turn isparallel to the (horizontal) plane of the workpiece 56 except at a stepor transition 44 a between turns (from one horizontal plane to thenext).

[0058] The cylindrical chamber 40 consists of a cylindrical side wall 50and a circular ceiling 52 integrally formed with the side wall 50 sothat the side wall 50 and ceiling 52 constitute a single piece ofmaterial, such as silicon. However, the invention may be carried outwith the side wall 50 and ceiling 52 formed as separate pieces, as willbe described later in this specification. The circular ceiling 52 may beof any suitable cross-sectional shape such as planar (FIG. 4A), dome(FIG. 4C), conical (FIG. 4D), truncated conical (FIG. 4E), cylindricalor any combination of such shapes or curve of rotation. Such acombination will be discussed later in this specification. Generally,the vertical pitch of the solenoid 42 (i.e., its vertical height dividedby its horizontal width) exceeds the vertical pitch of the ceiling 52,even for ceilings defining 3-dimensional surfaces such as dome, conical,truncated conical and so forth. The purpose for this, at least in thepreferred embodiment, is to concentrate the induction of the antennanear the antenna symmetry axis, as discussed previously in thisspecification. A solenoid having a pitch exceeding that of the ceiling52 is referred to herein as a non-conformal solenoid, meaning that, ingeneral, its shape does not conform with the shape of the ceiling, andmore specifically that its vertical pitch exceeds the vertical pitch ofthe ceiling. A 2-dimensional or flat ceiling has a vertical pitch ofzero, while a 3-dimensional ceiling has a non-zero vertical pitch.

[0059] A pedestal 54 at the bottom of the chamber 40 supports a planarworkpiece 56 in a workpiece support plane during processing. Theworkpiece 56 is typically a semiconductor wafer and the workpiecesupport plane is generally the plane of the wafer or workpiece 56. Thechamber 40 is evacuated by a pump (not shown in the drawing) through anannular passage 58 to a pumping annulus 60 surrounding the lower portionof the chamber 40. The interior of the pumping annulus may be lined witha replaceable metal liner 60 a. The annular passage 58 is defined by thebottom edge 50 a of the cylindrical side wall 50 and a planar ring 62surrounding the pedestal 54. Process gas is furnished into the chamber40 through any one or all of a variety of gas feeds. In order to controlprocess gas flow near the workpiece center, a center gas feed 64 a canextend downwardly through the center of the ceiling 52 toward the centerof the workpiece 56 (or the center of the workpiece support plane). Inorder to control gas flow near the workpiece periphery (or near theperiphery of the workpiece support plane), plural radial gas feeds 64 b,which can be controlled independently of the center gas feed 64 a,extend radially inwardly from the side wall 50 toward the workpieceperiphery (or toward the workpiece support plane periphery), or baseaxial gas feeds 64 c extend upwardly from near the pedestal 54 towardthe workpiece periphery, or ceiling axial gas feeds 64 d can extenddownwardly from the ceiling 52 toward the workpiece periphery. Etchrates at the workpiece center and periphery can be adjustedindependently relative to one another to achieve a more radially uniformetch rate distribution across the workpiece by controlling the processgas flow rates toward the workpiece center and periphery through,respectively, the center gas feed 64 a and any one of the outer gasfeeds 64 b-d. This feature of the invention can be carried out with thecenter gas feed 64 a and only one of the peripheral gas feeds 64 b-d.

[0060] The solenoidal coil antenna 42 is wound around a housing 66surrounding the center gas feed 64 a. A plasma source RF power supply 68is connected across the coil antenna 42 and a bias RF power supply 70 isconnected to the pedestal 54.

[0061] Confinement of the overhead coil antenna 42 to the center regionof the ceiling 52 leaves a large portion of the top surface of theceiling 52 unoccupied and therefore available for direct contact withtemperature control apparatus including, for example, plural radiantheaters 72 such as tungsten halogen lamps and a water-cooled cold plate74 which may be formed of copper or aluminum for example, with coolantpassages 74 a extending therethrough. Preferably the coolant passages 74a contain a coolant of a known variety having a high thermalconductivity but a low electrical conductivity, to avoid electricallyloading down the antenna or solenoid 42. The cold plate 74 providesconstant cooling of the ceiling 52 while the maximum power of theradiant heaters 72 is selected so as to be able to overwhelm, ifnecessary, the cooling by the cold plate 74, facilitating responsive andstable temperature control of the ceiling 52. The large ceiling areairradiated by the heaters 72 provides greater uniformity and efficiencyof temperature control. (It should be noted that radiant heating is notnecessarily required in carrying out the invention, and the skilledworker may choose to employ an electric heating element instead, as willbe described later in this specification.) If the ceiling 52 is silicon,as disclosed in co-pending U.S. application Ser. No. 08/597,577 filedFeb. 2, 1996 by Kenneth S. Collins et al., then there is a significantadvantage to be gained by thus increasing the uniformity and efficiencyof the temperature control across the ceiling. Specifically, where apolymer precursor and etchant precursor process gas (e.g., afluorocarbon gas) is employed and where the etchant (e.g., fluorine)must be scavenged, the rate of polymer deposition across the entireceiling 52 and/or the rate at which the ceiling 52 furnishes a fluorineetchant scavenger material (silicon) into the plasma is bettercontrolled by increasing the contact area of the ceiling 52 with thetemperature control heater 72. The solenoid antenna 42 increases theavailable contact area on the ceiling 52 because the solenoid windings44 are concentrated at the center axis of the ceiling 52.

[0062] The increase in available area on the ceiling 52 for thermalcontact is exploited in a preferred implementation by a highly thermallyconductive torus 75 (formed of a ceramic such as aluminum nitride,aluminum oxide or silicon nitride or of a non-ceramic like siliconeither lightly doped or undoped) whose bottom surface rests on theceiling 52 and whose top surface supports the cold plate 74. One featureof the torus 75 is that it displaces the cold plate 74 well-above thetop of the solenoid 42. This feature substantially mitigates or nearlyeliminates the reduction in inductive coupling between the solenoid 42and the plasma which would otherwise result from a close proximity ofthe conductive plane of the cold plate 74 to the solenoid 42. In orderto prevent such a reduction in inductive coupling, it is preferable thatthe distance between the cold plate 74 and the top winding of thesolenoid 42 be at least a substantial fraction (e.g., one half) of thetotal height of the solenoid 42. Plural axial holes 75 a extendingthrough the torus 75 are spaced along two concentric circles and holdthe plural radiant heaters or lamps 72 and permit them to directlyirradiate the ceiling 52. For greatest lamp efficiency, the holeinterior surface may be lined with a reflective (e.g., aluminum) layer.The center gas feed 64 a of FIG. 4A may be replaced by a radiant heater72 (as shown in FIG. 5), depending upon the particular reactor designand process conditions. The ceiling temperature is sensed by a sensorsuch as a thermocouple 76 extending through one of the holes 75 a notoccupied by a lamp heater 72. For good thermal contact, a highlythermally conductive elastomer 73 such as silicone rubber impregnatedwith boron nitride is placed between the ceramic torus 75 and the coppercold plate 74 and between the ceramic torus 75 and the silicon ceiling52.

[0063] As disclosed in the above-referenced co-pending application, thechamber 40 may be an all-semiconductor chamber, in which case theceiling 52 and the side wall 50 are both a semiconductor material suchas silicon. As described in the above-referenced co-pending application,controlling the temperature of, and RF bias power applied to, either theceiling 52 or the wall 50 regulates the extent to which it furnishesfluorine scavenger precursor material (silicon) into the plasma or,alternatively, the extent to which it is coated with polymer. Thematerial of the ceiling 52 is not limited to silicon but may be, in thealternative, silicon carbide, silicon dioxide (quartz), silicon nitrideor a ceramic.

[0064] As described in the above-referenced co-pending application, thechamber wall or ceiling 50, 52 need not be used as the source of afluorine scavenger material. Instead, a disposable silicon member can beplaced inside the chamber 40 and maintained at a sufficiently hightemperature to prevent polymer condensation thereon and permit siliconmaterial to be removed therefrom into the plasma as fluorine scavengingmaterial. In this case, the wall 50 and ceiling 52 need not necessarilybe silicon, or if they are silicon they may be maintained at atemperature (and/or RF bias) near or below the polymer condensationtemperature (and/or a polymer condensation RF bias threshold) so thatthey are coated with polymer from the plasma so as to be protected frombeing consumed. While the disposable silicon member may take anyappropriate form, in the embodiment of FIG. 4A the disposable siliconmember is an annular ring 62 surrounding the pedestal 54. Preferably,the annular ring 62 is high purity silicon and may be doped to alter itselectrical or optical properties. In order to maintain the silicon ring62 at a sufficient temperature to ensure its favorable participation inthe plasma process (e.g., its contribution of silicon material into theplasma for fluorine scavenging), plural radiant (e.g., tungsten halogenlamp) heaters 77 arranged in a circle under the annular ring 62 heat thesilicon ring 62 through a quartz window 78. As described in theabove-referenced co-pending application, the heaters 77 are controlledin accordance with the measured temperature of the silicon ring 62sensed by a temperature sensor 79 which may be a remote sensor such asan optical pyrometer or a fluoro-optical probe. The sensor 79 may extendpartially into a very deep hole 62 a in the ring 62, the deepness andnarrowness of the hole tending at least partially to masktemperature-dependent variations in thermal emissivity of the siliconring 62, so that it behaves more like a gray-body radiator for morereliable temperature measurement.

[0065] As described in U.S. application Ser. No. 08/597,577 referred toabove, an advantage of an all-semiconductor chamber is that the plasmais free of contact with contaminant producing materials such as metal,for example. For this purpose, plasma confinement magnets 80, 82adjacent the annular opening 58 prevent or reduce plasma flow into thepumping annulus 60. To the extent any polymer precursor and/or activespecies succeeds in entering the pumping annulus 60, any resultingpolymer or contaminant deposits on the replaceable interior liner 60 amay be prevented from re-entering the plasma chamber 40 by maintainingthe liner 60 a at a temperature significantly below the polymercondensation temperature, for example, as disclosed in the referencedco-pending application.

[0066] A wafer slit valve 84 through the exterior wall of the pumpingannulus 60 accommodates wafer ingress and egress. The annular opening 58between the chamber 40 and pumping annulus 60 is larger adjacent thewafer slit valve 84 and smallest on the opposite side by virtue of aslant of the bottom edge 50 a of the cylindrical side wall 50 so as tomake the chamber pressure distribution more symmetrical with anon-symmetrical pump port location.

[0067] Maximum inductance near the chamber center axis 46 is achieved bythe vertically stacked solenoidal windings 44. In the embodiment of FIG.4A, another winding 45 outside of the vertical stack of windings 44 butin the horizontal plane of the bottom solenoidal winding 44 b may beadded, provided the additional winding 45 is close to the bottomsolenoidal winding 44 b.

[0068] Referring specifically now to the preferred dual solenoidembodiment of FIG. 5, a second outer vertical stack or solenoid 90 ofwindings 92 at an outer location (i.e, against the outer circumferentialsurface of the thermally conductive torus 75) is displaced by a radialdistance OR from the inner vertical stack of solenoidal windings 44.Note that in FIG. 5 confinement of the inner solenoidal antenna 42 tothe center and the outer solenoidal antenna 90 to the periphery leaves alarge portion of the top surface of the ceiling 52 available for directcontact with the temperature control apparatus 72, 74, 75, as in FIG.4A. An advantage is that the larger surface area contact between theceiling 52 and the temperature control apparatus provides a moreefficient and more uniform temperature control of the ceiling 52.

[0069] For a reactor in which the side wall 50 and ceiling 52 are formedof a single piece of silicon for example with an inside diameter of 12.6in (32 cm), the wafer-to-ceiling gap is 3 in (7.5 cm), and the meandiameter of the inner solenoid was 3.75 in (9.3 cm) while the meandiameter of the outer solenoid was 11.75 in (29.3 cm) using {fraction(3/16)} in diameter hollow copper tubing covered with a 0.03 thickteflon insulation layer, each solenoid consisting of four turns andbeing 1 in (2.54 cm) high. The outer stack or solenoid 90 is energizedby a second independently controllable plasma source RF power supply 96.The purpose is to permit different user-selectable plasma source powerlevels to be applied at different radial locations relative to theworkpiece or wafer 56 to permit compensation for known processingnon-uniformities across the wafer surface, a significant advantage. Incombination with the independently controllable center gas feed 64 a andperipheral gas feeds 64 b-d, etch performance at the workpiece centermay be adjusted relative to etch performance at the edge by adjustingthe RF power applied to the inner solenoid 42 relative to that appliedto the outer solenoid 90 and adjusting the gas flow rate through thecenter gas feed 64 a relative to the flow rate through the outer gasfeeds 64 b-d. While the present invention solves or at least amelioratesthe problem of a center null or dip in the inductance field as describedabove, there may be other plasma processing non-uniformity problems, andthese can be compensated in the versatile embodiment of FIG. 5 byadjusting the relative RF power levels applied to the inner and outerantennas 42, 90. For effecting this purpose with greater convenience,the respective RF power supplies 68, 96 for the inner and outersolenoids 42, 90 may be replaced by a common power supply 97 a and apower splitter 97 b which permits the user to change the relativeapportionment of power between the inner and outer solenoids 42, 90while preserving a fixed phase relationship between the fields of theinner and outer solenoids 42, 90. This is particularly important wherethe two solenoids 42, 90 receive RF power at the same frequency.Otherwise, if the two independent power supplies 68, 96 are employed,then they may be powered at different RF frequencies, in which case itis preferable to install RF filters at the output of each RF powersupply 68, 96 to avoid off-frequency feedback from coupling between thetwo solenoids. In this case, the frequency difference should besufficient to time-average out coupling between the two solenoids and,furthermore, should exceed the rejection bandwidth of the RF filters.Another option is to make each frequency independently resonantlymatched to the respective solenoid, and each frequency may be varied tofollow changes in the plasma impedance (thereby maintaining resonance)in lieu of conventional impedance matching techniques. In other words,the RF frequency applied to the antenna is made to follow the resonantfrequency of the antenna as loaded by the impedance of the plasma in thechamber. In such implementations, the frequency ranges of the twosolenoids should be mutually exclusive. Preferably, however, the twosolenoids are driven at the same RF frequency and in this case it ispreferable that the phase relationship between the two be such as tocause constructive interaction or superposition of the fields of the twosolenoids. Generally, this requirement will be met by a zero phase anglebetween the signals applied to the two solenoids if they are both woundin the same sense. Otherwise, if they are oppositely wound, the phaseangle is preferably 180□. In any case, coupling between the inner andouter solenoids can be minimized or eliminated by having a relativelylarge space between the inner and outer solenoids 42, 90, as will bediscussed below in this specification.

[0070] The range attainable by such adjustments is increased byincreasing the radius of the outer solenoid 90 to increase the spacingbetween the inner and outer solenoids 42, 90, so that the effects of thetwo solenoids 42, 90 are more confined to the workpiece center and edge,respectively. This permits a greater range of control in superimposingthe effects of the two solenoids 42, 90. For example, the radius of theinner solenoid 42 should be no greater than about half the workpieceradius and preferably no more than about a third thereof. (The minimumradius of the inner solenoid 42 is affected in part by the diameter ofthe conductor forming the solenoid 42 and in part by the need to providea finite non-zero circumference for an arcuate—e.g., circular—currentpath to produce inductance.) The radius of the outer coil 90 should beat least equal to the workpiece radius and preferably 1.5 or more timesthe workpiece radius. With such a configuration, the respective centerand edge effects of the inner and outer solenoids 42, 90 are sopronounced that by increasing power to the inner solenoid the chamberpressure can be raised into the hundreds of mT while providing a uniformplasma, and by increasing power to the outer solenoid 90 the chamberpressure can be reduced to on the order of 0.01 mT while providing auniform plasma. Another advantage of such a large radius of the outersolenoid 90 is that it minimizes coupling between the inner and outersolenoids 42, 90.

[0071]FIG. 5 indicates in dashed line that a third solenoid 94 may beadded as an option, which is desireable for a very large chamberdiameter.

[0072]FIG. 6 illustrates a variation of the embodiment of FIG. 5 inwhich the outer solenoid 90 is replaced by a planar winding 100.

[0073]FIG. 7A illustrates a variation of the embodiment of FIG. 4A inwhich the center solenoidal winding includes not only the vertical stack42 of windings 44 but in addition a second vertical stack 102 ofwindings 104 closely adjacent to the first stack 42 so that the twostacks constitute a double-wound solenoid 106. Referring to FIG. 7B, thedoubly wound solenoid 106 may consist of two independently wound singlesolenoids 42, 102, the inner solenoid 42 consisting of the windings 44a, 44 b, and so forth and the outer solenoid 102 consisting of thewinding 104 a, 104 b and so forth. Alternatively, referring to FIG. 7C,the doubly wound solenoid 106 may consist of vertically stacked pairs ofat least nearly co-planar windings. In the alternative of FIG. 7C, eachpair of nearly co-planar windings (e.g., the pair 44 a, 104 a or thepair 44 b, 104 b) may be formed by helically winding a single conductor.The term “doubly wound” used herein refers to winding of the type shownin either FIG. 7B or 7C. In addition, the solenoid winding may not bemerely doubly wound but may be triply wound or more and in general itcan consists of plural windings at each plane along the axis ofsymmetry. Such multiple-wound solenoids may be employed in either one orboth the inner and outer solenoids 42, 90 of the dual-solenoidembodiment of FIG. 5.

[0074]FIG. 8 illustrates a variation of the embodiment of FIG. 7A inwhich an outer doubly wound solenoid 110 concentric with the innerdoubly wound solenoid 106 is placed at a radial distance δR from theinner solenoid 106.

[0075]FIG. 9 illustrates a variation of the embodiment of FIG. 8 inwhich the outer doubly wound solenoid 110 is replaced by an ordinaryouter solenoid 112 corresponding to the outer solenoid employed in theembodiment of FIG. 5.

[0076]FIG. 10 illustrates another preferred embodiment in which thesolenoid 42 of FIG. 5 is placed at a location displaced by a radialdistance δR from the center gas feed housing 66. In the embodiment ofFIG. 4A, δR is zero while in the embodiment of FIG. 10 δR is asignificant fraction of the radius of the cylindrical side wall 50.Increasing δR to the extent illustrated in FIG. 10 may be helpful as analternative to the embodiments of FIGS. 4A, 5, 7A and 8 for compensatingfor non-uniformities in addition to the usual center dip in plasma iondensity described with reference to FIGS. 3D and 3E. Similarly, theembodiment of FIG. 10 may be helpful where placing the solenoid 42 atthe minimum distance from the chamber center axis 46 (as in FIG. 4)would so increase the plasma ion density near the center of the wafer 56as to over-correct for the usual dip in plasma ion density near thecenter and create yet another non-uniformity in the plasma processbehavior. In such a case, the embodiment of FIG. 10 is preferred whereδR is selected to be an optimum value which provides the greatestuniformity in plasma ion density. Ideally in this case, δR is selectedto avoid both under-correction and over-correction for the usual centerdip in plasma ion density. The determination of the optimum value for δRcan be carried out by the skilled worker by trial and error steps ofplacing the solenoid 42 at different radial locations and employingconventional techniques to determine the radial profile of the plasmaion density at each step.

[0077]FIG. 11 illustrates an embodiment in which the solenoid 42 has aninverted conical shape while FIG. 12 illustrates an embodiment in whichthe solenoid 42 has an upright conical shape.

[0078]FIG. 13 illustrates an embodiment in which the solenoid 42 iscombined with a planar helical winding 120. The planar helical windinghas the effect of reducing the severity with which the solenoid winding42 concentrates the induction field near the center of the workpiece bydistributing some of the RF power somewhat away from the center. Thisfeature may be useful in cases where it is necessary to avoidovercorrecting for the usual center null. The extent of such diversionof the induction field away from the center corresponds to the radius ofthe planar helical winding 120. FIG. 14 illustrates a variation of theembodiment of FIG. 13 in which the solenoid 42 has an inverted conicalshape as in FIG. 11. FIG. 15 illustrates another variation of theembodiment of FIG. 13 in which the solenoid 42 has an upright conicalshape as in the embodiment of FIG. 12.

[0079] The RF potential on the ceiling 52 may be increased, for exampleto prevent polymer deposition thereon, by reducing its effectivecapacitive electrode area relative to other electrodes of the chamber(e.g., the workpiece and the sidewalls). FIG. 16 illustrates how thiscan be accomplished by supporting a smaller-area version of the ceiling52′ on an outer annulus 200, from which the smaller-area ceiling 52′ isinsulated. The annulus 200 may be formed of the same material (e.g.,silicon) as the ceiling 52′ and may be of a truncated conical shape(indicated in solid line) or a truncated dome shape (indicated in dashedline). A separate RF power supply 205 may be connected to the annulus200 to permit more workpiece center versus edge process adjustments.

[0080]FIG. 17A illustrates a variation of the embodiment of FIG. 5 inwhich the ceiling 52 and side wall 50 are separate semiconductor (e.g.,silicon) pieces insulated from one another having separately controlledRF bias power levels applied to them from respective RF sources 210, 212to enhance control over the center etch rate and selectivity relative tothe edge. As set forth in greater detail in above-referenced U.S.application Ser. No. 08/597,577 filed Feb. 2, 1996 by Kenneth S. Collinset al., the ceiling 52 may be a semiconductor (e.g., silicon) materialdoped so that it will act as an electrode capacitively coupling the RFbias power applied to it into the chamber 40 and simultaneously as awindow through which RF power applied to the solenoid 42 may beinductively coupled into the chamber 40. The advantage of such awindow-electrode is that an RF potential may be established directlyover the wafer 56 (e.g., for controlling ion energy) while at the sametime inductively coupling RF power directly over the wafer 56. Thislatter feature, in combination with the separately controlled inner andouter solenoids 42, 90 and center and peripheral gas feeds 64 a, 64 b-dgreatly enhances the ability to adjust various plasma process parameterssuch as ion density, ion energy, etch rate and etch selectivity at theworkpiece center relative to the workpiece edge to achieve an optimumuniformity. In this combination, the respective gas flow rates throughindividual gas feeds are individually and separately controlled toachieve such optimum uniformity of plasma process parameters.

[0081]FIG. 17A illustrates how the lamp heaters 72 may be replaced byelectric heating elements 72′. As in the embodiment of FIG. 4A, thedisposable silicon member is an annular ring 62 surrounding the pedestal54.

[0082]FIG. 17B illustrates another variation in which the ceiling 52itself may be divided into an inner disk 52 a and an outer annulus 52 belectrically insulated from one another and separately biased byindependent RF power sources 214, 216 which may be separate outputs of asingle differentially controlled RF power source.

[0083] In accordance with an alternative embodiment, a user-accessiblecentral controller 300 shown in FIGS. 17A and 17B, such as aprogrammable electronic controller including, for example, aconventional microprocessor and memory, is connected to simultaneouslycontrol gas flow rates through the central gas feed 64 a and theperipheral gas feeds 64 b-d, RF plasma source power levels applied tothe inner and outer antennas 42, 90 and RF bias power levels applied tothe ceiling 52 and side wall 50 respectively (in FIG. 17A) and the RFbias power levels applied to the inner and outer ceiling portions 52 a,52 b (in FIG. 17B), temperature of the ceiling 52 and the temperature ofthe silicon ring 62. A ceiling temperature controller 218 governs thepower applied by a power source 220 to the heaters 72′ by comparing thetemperature measured by the ceiling temperature sensor 76 with a desiredtemperature known to the controller 300. A ring temperature controller222 controls the power applied by a heater power source 224 to theheater lamps 77 facing the silicon ring 62 by comparing the ringtemperature measured by the ring sensor 79 with a desired ringtemperature stored known to the controller 222. The master controller300 governs the desired temperatures of the temperature controllers 218and 222, the RF power levels of the solenoid power sources 68, 96, theRF power levels of the bias power sources 210, 212 (FIG. 17A) or 214,216 (FIG. 17B), the wafer bias level applied by the RF power source 70and the gas flow rates supplied by the various gas supplies (or separatevalves) to the gas inlets 64 a-d. The key to controlling the wafer biaslevel is the RF potential difference between the wafer pedestal 54 andthe ceiling 52. Thus, either the pedestal RF power source 70 or theceiling RF power source 210 may be simply a short to RF ground. Withsuch a programmable integrated controller, the user can easily optimizeapportionment of RF source power, RF bias power and gas flow ratebetween the workpiece center and periphery to achieve the greatestcenter-to-edge process uniformity across the surface of the workpiece(e.g., uniform radial distribution of etch rate and etch selectivity).Also, by adjusting (through the controller 300) the RF power applied tothe solenoids 42, 90 relative to the RF power difference between thepedestal 54 and ceiling 52, the user can operate the reactor in apredominantly inductively coupled mode or in a predominantlycapacitively coupled mode.

[0084] While the various power sources connected in FIG. 17A to thesolenoids 42, 90, the ceiling 52, side wall 50 (or the inner and outerceiling portions 52 a, 52 b as in FIG. 17B) have been described asoperating at RF frequencies, the invention is not restricted to anyparticular range of frequencies, and frequencies other than RF may beselected by the skilled worker in carrying out the invention.

[0085] In a preferred embodiment of the invention, the high thermalconductivity spacer 75, the ceiling 52 and the side wall 50 areintegrally formed together from a single piece of crystalline silicon.

[0086] While the invention has been described as being carried out witha number of separate RF sources, some or all of the RF sources depictedherein may derive their outputs from separate RF generators or from acommon RF generator with different outputs at different RF power levels,frequencies and phases synthesized with variable power dividers,frequency multipliers and/or phase delays, as may be appropriate.Moreover, while the invention has been described as being carried outwith a number of separate process gas supplies, some or all of theprocess gas supplies may be derived from a common process gas supplywhich is divided among the plural separately controlled gas inlets 64.

[0087] While the invention has been described in detail by specificreference to preferred embodiments, it is understood that variations andmodifications thereof may be made without departing from the true spiritand scope of the invention.

What is claimed is:
 1. A plasma chamber enclosure structure for use inan RF plasma reactor which includes a pedestal adapted to support aworkpiece to be processed, a reactor base housing the pedestal, and acoil antenna adjacent the reactor and which is adapted to inductivelycouple RF power into the reactor, said plasma chamber enclosurestructure comprising: a) said plasma chamber enclosure structure being asingle-wall dielectric enclosure structure; b) said plasma chamberenclosure structure being of an inverted cup-shape configuration; c)said plasma chamber enclosure structure comprising a ceiling comprising:(i) a centrally located gas inlet; and (ii) an interior surface ofsubstantially flat conical configuration extending to said gas inletsuch that when positioned over the base said interior surface is moredistant from the pedestal over a center of the pedestal and closer tothe pedestal over a periphery of the pedestal; d) said plasma chamberenclosure structure having a sidewall, said sidewall comprising: (i) alower cylindrical portion generally transverse to the pedestal whenpositioned over the base; and (ii) a transitional portion between saidlower cylindrical portion and said ceiling, said transitional portionextending inwardly from said lower cylindrical portion, saidtransitional portion comprising a radius of curvature; e) said plasmachamber enclosure structure being adapted to cover the reactor base tocomprise the RF plasma reactor; f) said plasma chamber enclosurestructure being adapted to define a plasma-processing volume over thepedestal; g) said plasma chamber enclosure structure being capable oftransmitting inductive power therethrough from an adjacent antenna; andh) said plasma chamber enclosure structure being formed of a dielectricmaterial selected from a group consisting of silicon, silicon carbide,quartz, and alumina.
 2. The enclosure structure of claim 1 being adaptedto be positioned adjacent the antenna.
 3. The enclosure structure ofclaim 2 wherein said dielectric material consists of alumina.
 4. Theenclosure structure of claim 1 wherein said dielectric material consistsof alumina.
 5. The enclosure structure of claim 1 wherein saiddielectric material comprises alumina.
 6. The enclosure structure ofclaim 1 wherein said top wall and said side wall consist of silicon. 7.The enclosure structure of claim 1 further comprising a conductiveceiling portion in a facing relationship to the pedestal when positionedover the base.
 8. The enclosure structure of claim 7 wherein saidconductive ceiling portion is adapted to be coupled to a bias powersource.
 9. The enclosure structure of claim 1 wherein said ceilingcomprises conductive material and is adapted to be coupled to a biaspower source.
 10. The enclosure structure of claim 1 having a generallyright circular cylindrical configuration.
 11. A plasma chamber dome foran RF plasma reactor which includes a pedestal adapted to support aworkpiece to be processed, a reactor base housing the pedestal, and acoil antenna adjacent the reactor and which is adapted to inductivelycouple RF power into the reactor, said dome comprising: a) said domehaving an inverted cup-shape configuration having top and side walls ina generally right circular cylindrical configuration; b) said top wallcomprising: (i) a centrally located gas inlet; and (ii) a substantiallyflat interior surface extending to said gas inlet; c) said sidewallcomprising: (i) a lower cylindrical portion generally transverse to thepedestal when positioned over the base; and (ii) a transitional portionbetween said lower cylindrical portion and said top wall, saidtransitional portion extend inwardly from said lower cylindricalportion, said transitional portion comprising at least one radius ofcurvature; d) said dome being adapted so as to be capable of having saidtop wall in a facing relationship to the pedestal when positioned overthe base; e) said dome being adapted to define a plasma-processingvolume over the pedestal; f) said dome being adapted to cover thereactor base to comprise the RF plasma reactor; g) said dome beingcapable of transmitting inductive power therethrough from an adjacentantenna; and h) said top wall and said side wall being formed of adielectric material selected from a group consisting of silicon, siliconcarbide, quartz, alumina, and sapphire.
 12. The plasma chamber dome ofclaim 11 wherein said top wall and said side wall consist of silicon.13. The plasma chamber dome of claim 11 wherein said top wall and saidside wall consist of alumina.
 14. The plasma chamber dome of claim 11wherein said substantially flat interior surface is a flattened conicalconfiguration such that when positioned over the base said interiorsurface is more distant from the pedestal over a center of the pedestaland closer to the pedestal over a periphery of the pedestal.
 15. Theplasma chamber dome of claim 11 further comprising a flange portionextending radially outward from said side wall.
 16. The plasma chamberdome of claim 15 wherein said top wall and said side wall consist ofsilicon.
 17. The plasma chamber dome of claim 15 wherein said top walland said side wall consist of alumina.
 18. The plasma chamber dome ofclaim 11 wherein said top wall and said side wall comprises alumina. 19.The plasma chamber dome of claim 11 comprising a conductive ceilingportion in a facing relationship to the pedestal when positioned overthe base.
 20. The plasma chamber dome of claim 19 wherein saidconductive ceiling portion is adapted to be coupled to a bias powersource.
 21. The plasma chamber dome of claim 11 wherein said top wallcomprises conductive material, said top wall being adapted to be coupledto a bias power source.
 22. An RF plasma reactor which includes apedestal adapted to support a workpiece to be processed, a reactor basehousing the pedestal, and a coil antenna adjacent the reactor and whichis adapted to inductively couple RF power into the reactor, the reactorcomprising: a) a single-wall dielectric enclosure structure of aninverted cup-shaped configuration having a ceiling comprising acentrally located gas inlet and comprising an interior surfacecomprising a substantially flat conical configuration extending to saidgas inlet; b) said single-wall dielectric enclosure structure having aside wall comprising a cylindrical portion generally transverse to thepedestal when positioned over the base and comprising a transitionportion extending inward from said cylindrical portion, said transitionportion comprising at least one radius of curvature; c) said single-walldielectric enclosure structure being adapted to cover the reactor baseto comprise the RF plasma reactor; d) said single-wall dielectricenclosure structure being adapted to define a plasma-processing volumeover the pedestal; e) said single-wall dielectric enclosure structurebeing capable of transmitting inductive power therethrough from anadjacent antenna; and f) said single-wall dielectric enclosure structurebeing formed of a dielectric material selected from a group consistingof silicon, silicon carbide, quartz, and alumina.
 23. The reactor ofclaim 22 wherein said ceiling when position over the base is in spacedfacing relationship to the pedestal.
 24. The reactor of claim 23 whereinsaid enclosure structure consists of alumina.
 25. The reactor of claim23 wherein said enclosure structure comprises alumina.
 26. The reactorof claim 23 said side wall is adapted to be positioned adjacent theantenna.
 27. The reactor of claim 22 wherein said enclosure structurehas a generally right circular cylindrical configuration.
 28. Thereactor of claim 22 wherein said dielectric consists of alumina.
 29. Thereactor of claim 22 wherein said dielectric comprises alumina.
 30. Thereactor of claim 22 comprising a conductive ceiling portion in a facingrelationship to the pedestal when positioned over the base.
 31. Thereactor of claim 30 wherein said conductive ceiling portion is adaptedto be coupled to a bias power source.
 32. The reactor of claim 22wherein said ceiling comprises a conductive material and is adapted tobe coupled to a bias power source.
 33. A plasma chamber enclosurestructure for use in an RF plasma reactor which includes a pedestaladapted to support a workpiece to be processed, a reactor base housingthe pedestal, and a coil antenna adjacent the reactor and which isadapted to inductively couple RF power into the reactor, said plasmachamber enclosure structure comprising: a) said plasma chamber enclosurestructure being a single-wall dielectric enclosure structure; b) saidplasma chamber enclosure structure being of an inverted cup-shapeconfiguration; c) said plasma chamber enclosure structure having asubstantially flat top central portion; d) said plasma chamber enclosurestructure being adapted to cover the reactor base to comprise the RFplasma reactor; e) said plasma chamber enclosure structure being adaptedto define a plasma-processing volume over the pedestal; f) said plasmachamber enclosure structure being capable of transmitting inductivepower therethrough from an adjacent antenna; and g) said plasma chamberenclosure structure being formed of a dielectric material selected fromthe group consisting of silicon, silicon carbide, quartz, and alumina.34. The enclosure structure of claim 33 being adapted so as to becapable of having said flat top central portion in a facing relationshipto the pedestal when positioned over the base.
 35. The enclosurestructure of claim 34 having a side wall generally transverse to saidflat top central portion.
 36. The enclosure structure of claim 35 beingadapted to be positioned adjacent the antenna.
 37. The enclosurestructure of claim 36 wherein said dielectric material consists ofalumina.
 38. The enclosure structure of claim 36 wherein said dielectricmaterial comprises alumina.
 39. The enclosure structure of claim 33having a generally right circular cylindrical configuration.
 40. Theenclosure structure of claim 33 wherein said dielectric materialconsists of alumina.
 41. The enclosure structure of claim 33 whereinsaid dielectric material comprises alumina.
 42. The enclosure structureof claim 33 further comprising a conductive ceiling portion in a facingrelationship to the pedestal when positioned over the base.
 43. Theenclosure structure of claim 40 wherein said conductive ceiling portionis adapted to be coupled to a bias power source.
 44. A plasma chamberdome for an RF plasma reactor which includes a pedestal adapted tosupport a workpiece to be processed, a reactor base housing thepedestal, and a coil antenna adjacent the reactor and which is adaptedto inductively couple RF power into the reactor, said dome comprising:a) said dome having an inverted cup-shape configuration having top andside walls in a generally right circular cylindrical configuration; b)said top wall comprising a flat central portion; c) said dome beingadapted so as to be capable of having said flat central portion in afacing relationship to the pedestal when positioned over the base; d)said dome being adapted to define a plasma-processing volume over thepedestal; e) said dome being adapted to cover the reactor base tocomprise the RF plasma reactor; f) said dome being capable oftransmitting inductive power therethrough from an adjacent antenna; andg) said top wall and said side wall being formed of a dielectricmaterial selected from the group consisting of silicon, silicon carbide,quartz, alumina, and sapphire.
 45. The plasma chamber dome of claim 42wherein said top wall and said side wall consist of silicon.
 46. Theplasma chamber dome of claim 42 wherein said top wall and said side wallconsist of alumina.
 47. The plasma chamber dome of claim 42 wherein saidtop wall and said side wall comprises alumina.
 48. The plasma chamberdome of claim 42 further comprising a flange portion extending radiallyoutward from said side wall.
 49. The plasma chamber dome of claim 45wherein said top wall and said side wall consist of silicon.
 50. Theplasma chamber dome of claim 45 wherein said top wall and said side wallconsist of alumina.
 51. The plasma chamber dome of claim 45 wherein saidtop wall and said side wall comprises alumina.
 52. The plasma chamberdome of claim 42 comprising a conductive ceiling portion in a facingrelationship to the pedestal when positioned over the base.
 53. Theplasma chamber dome of claim 48 wherein said conductive ceiling portionis adapted to be coupled to a bias power source.
 54. An RF plasmareactor which includes a pedestal adapted to support a workpiece to beprocessed, a reactor base housing the pedestal, and a coil antennaadjacent the reactor and which is adapted to inductively couple RF powerinto the reactor, the reactor comprising: a) a single-wall dielectricenclosure structure of an inverted cup-shaped configuration having asubstantially flat top central portion; b) said single-wall dielectricenclosure structure being adapted to cover the reactor base to comprisethe RF plasma reactor; c) said single-wall dielectric enclosurestructure being adapted to define a plasma-processing volume over thepedestal; d) said single-wall dielectric enclosure structure beingcapable of transmitting inductive power therethrough from an adjacentantenna; and e) said single-wall dielectric enclosure structure beingformed of a dielectric material selected from the group consisting ofsilicon, silicon carbide, quartz, and alumina.
 55. The reactor of claim50 wherein said flat top central portion when position over the base isin spaced facing relationship to the pedestal.
 56. The reactor of claim51 wherein said enclosure structure has a side wall generally transverseto said top central flat portion.
 57. The reactor of claim 52 whereinsaid enclosure structure consists of alumina.
 58. The reactor of claim52 wherein said enclosure structure comprises alumina.
 59. The reactorof claim 51 wherein said enclosure structure has a side wall adapted tobe positioned adjacent the antenna.
 60. The reactor of claim 50 whereinsaid enclosure structure has a generally right circular cylindricalconfiguration.
 61. The reactor of claim 50 wherein said dielectricconsists of alumina.
 62. The reactor of claim 50 wherein said dielectriccomprises alumina.
 63. The reactor of claim 50 comprising a conductiveceiling portion in a facing relationship to the pedestal when positionedover the base.
 64. The reactor of claim 57 wherein said conductiveceiling portion is adapted to be coupled to a bias power source.